The salivary immune response to oral antigens may modulate the number and type of microorganisms which colonize the oral cavity. These responses may be elicited by exposure to antigen in the gut or by exposure of lymphtic tissue in the oral cavity, for example, in minor salivary glands. An understanding of the development of immunocompetence in the infant and young child, and an identifiction of the ages at which children first respond to oral streptococci, such as S. salivrius, knowlegeable fashion. Glucosyltransferases are extracellular products of these streptococci which synethesize glucans, some of which have been implicated in the cariogenicity of S. mutans. To this end, the present investigtion proposes to measure the longitudinal development of IgA antibody levels to glucosyltransferase antigens from S. salivrius, S. sanguis, and S. mutans in whole salivas of infants and children up to five years of age. The presence of these oral streptococci will also be ascertained by selective plating of plaque or oral mucosa in order to identify the irst appearance of these streptococci. The identification of these microorganisms will be correlated with antibody levels to the repective antigens. The distribution of isotypes of salivary antibody, especially in salivas from children younger than six months, will be investigted by high pressure liquid chromatography and enzyme-linked immunosorben assay (ELISA). The antigenic challenge of infants at 2,4 and 6 months of age with oral polio vaccine and parenteral DPT vaccine represents a useful model for exploring immune responses during the development of immuocompetance in the oral cavity. Thus, a longitudinal study of the appearance and changes in salivary antibody levels to poliovirus typs 1, 2 and 3 and to tetanus toxoid will be conducted in children up to five yers of age. Finally, the ability to elicit a local immune response in the oral cavity will be investigated by application of tetanus toxoid to the labial mucosae. Responses will be measured by ELISA in labial minor gland secretions. These data should reveal the potential for local antigenic stimulation in the oral cavity and the use of this route for future immunization protocols.